The Deployment of a low-Earth-orbit Space Station and the onset of advanced missions will necessitate significant requirements of metabolic oxygen (O.sub.2) for Extravehicular Activity (EVA). This O.sub.2 must be supplied at high pressure (i.e., up to 41,368 kPa (6,000 psia)) to refill EVA O.sub.2 bottles. Due to the weight, volume and logistic penalties associated with high pressure O.sub.2 resupply and storage, alternative technologies which utilize on-board Space Station resources (i.e., electricity and water) such as water electrolysis systems are preferable. The Solid Metal Cathode (SMC) water electrolysis concept offers the capability to generate high pressure O.sub.2 directly, thus minimizing system complexity and eliminating the need for a separate mechanical compressor. The key problem involved in this effort included the development of a water electrolysis concept which would be capable of safely and reliably generating high pressure O.sub.2. The prior technique utilized for recharging the EVA O.sub.2 bottles consists of supplying expendable O.sub.2 bottles with each mission. Upon completion of the mission, the O.sub.2 bottles are recovered and recharged. The primary limitation of the prior technique is that the weight, volume and logistic penalties associated with high pressure O.sub.2 transportation and storage become prohibitive for long-term missions. Since these missions will be feature extensive EVA, it is essential that an alternative method be utilized. In this context, the present disclosure is directed to an airborne oxygen generator system and more particularly to one which incorporates a mechanism capable of forming oxygen in a space station in circumstances where gravity forces are either small or negligible. It forms oxygen as a gas by the electrolysis of water thereby liberating oxygen and hydrogen. The hydrogen is liberated in such a fashion that it does not pose a problem. Moreover, the oxygen generated by the system can be delivered against very high back pressures, with sufficient high pressure that oxygen generation provides its own substantial pressure drive to thereby simplify the system and avoid the necessity of a separate oxygen compressor or similar equipment, reducing the weight and complexity of the equipment.
The present disclosure sets out a system wherein a pair of spaced, preferably cylindrical or planar electrodes define an electrolysis cell. The two electrodes are separated by a space that is filled with water, and a suitable strong base placed in the water defines the necessary electrolyte. The water can be continuously consumed. The space between the electrodes may also be filled by a porous nonconductive media in which the water and suitably strong base are held by capillary forces. As water is converted into constituent gases, the water is replaced to keep the chamber filled. Moreover, the constituent gases are liberated at the spaced electrodes. One of the electrodes is porous while the other is a solid metal member. The solid metal electrode or terminal defines a pressure barrier so that one side can be maintained at a reduced or reference pressure while the other side is maintained at an elevated pressure. The elevated pressure enables delivery of the pressurized liberated oxygen to a pressure storage vessel without interposing a mechanical pump or compressor. Conveniently, the system is illustrated with a water supply and check valve to assure delivery of the necessary amount of water, and the gas which is liberated is delivered through a check valve into a storage container. Pressure regulators can be used to regulate the various segments when the equipment is not in use.
Known references include U.S. Pat. No. 3,711,385 which shows an electrode composed of palladium in an electrolytic cell.
U.S. Pat. No. 4,078,985 shows a hydrogen generator which is accomplished through the electrolysis of water. The apparatus consists of palladium or palladium alloys for the cathode material. A pipe is provided for the transmission of oxygen to the anode for collection. The object of this process is to produce a thin membrane cathode which prevents oxidation of the palladium and reduces electrical consumption.
U.S. Pat. No. 4,781,803 shows an electrolytic cell with a palladium cathode. The process is used for the disassociation of water into hydrogen and oxygen.
U.S. Pat. No. 4,793,910 shows an apparatus for the production of H.sub.2 and O.sub.2 by electrolysis. By making use of multiple membranes in parallel, the inventor claims to accomplish efficient photoelectrolysis. The membranes contain platinum.
U.S. Pat. No. 4,797,185 shows a fuel cell comprising a solid electrolyte to increase the mechanical strength of the apparatus. This cell appears to be the opposite process of the present disclosure.
By contrast, the present system sets forth a structure which is capable of attaining pressures as high as 6,000 psi across the cell. Moreover, this is accomplished so that the gas evolved has sufficient pressure drive of its own so that gas is delivered at an elevated pressure without a pump to overcome limitations on pressure in downstream delivery. In this context, the system is therefore a cell which both generates and pressurizes the oxygen which is necessary for operation of oxygen supported equipment or personnel aboard a space craft.